| 摘要 |
An improved drill bit for directional drilling includes a housing or headpiece having means at a rear end thereof for mounting the bit on a trailing component of a drill head, and passages for ejection of drilling fluid into a borehole. A first axle is mounted to extend forwardly from a front end of the housing, and a first roller is rotatably mounted on the first axle. The first roller has cutting projections such as carbide studs thereon and extends outside of the outer diameter of the housing by a distance which defines the size of the borehole when the drill bit is rotated over 360 degrees. A second axle is mounted to extend from the front end of the housing, and a second roller is rotatably mounted on the second axle at a position offset from the first axle. The second roller extends slightly outside of the outer diameter of the housing, but by a distance less than the distance the first roller extends outside of the housing. The second roller is configured to provide a reaction surface for the first roller as the first roller bores the borehole with the cutting projections. |
